Ferrous alloy



Patented Jan. 23, 1934 PATENT OFFICE FERBOUS ALLOY Victor 0. Homerberg, Belmont,

to The Nitromal Corporation,

Mass, assignor Albany, N. Y.,

a corporation of Delaware No Drawing. Application May 10, 1929 Serial No. 362,136 I 2 Claims. (01. 148 3l) My invention relates to ferrous alloys and particularly to white, mottled and malleable cast irons containing elements rendering them amenable to surface hardening by the nitriding process.

While it has been proposed to harden ordinary gray cast iron or steel by subjecting it to the action of ammonia at a temperature of from 900 to 1800 degrees Fahrenheit, experimental work along this line has indicated the impossibility of obtaining a product which, from a practical or commercial viewpoint, is satisfactory.

No appreciable hardening can be attained by nitriding ordinary cast iron at a temperature as low as 900 degrees F., nor can such iron be hardened to an appreciable degree by nitriding at temperatures as high as'1800 degrees F., without additional heat treatment. Furthermore, the case produced in either instance is brittle and susceptible to spalling and exfoliation.

It has also been proposed to harden gray cast iron alloys by the Fry nitriding process thereby attaining a final hardness said to correspond to that of hard chill castings or, in other words, to the hardness of white cast iron, to which this invention more particularly relates.

White cast iron is very difiicult or almost impossible to machine but can be malleableized and is adapted for many uses for which gray cast iron is wholly unsuited. When malleableized it may be machined, and if, thereafter, the surface portions subjected to wear can be appreciably hardened the field of application will be enormously extended. 0

In order to appreciably harden steel by nitriding, certain alloying elements, such as aluminum for example, and preferably other elements also, must be incorporated therein. It is not apparent that the addition to white cast iron of an alloying element or elements essential to nitriding and less than 2% of will not prevent the malleableizing of the iron, nor is it apparent that after malleableizing such a white cast iron alloy it can be again hardened by nitriding to a degree suificient to make a commercially desirable product,

I find, however, that the addition of small quantities of aluminum, say from 0.15% to 5.0% to a white cast iron having a total carbon content of from about 2.0% to 4.5% produces an alloy which can be malleableized and, moreover, can be satisfactorily nitride hardened at comparatively low temperatures.

To avoid warping and distortion in treating such a malleableized cast iron by the nitriding process it is extremely important that the operation be conducted at a temperature which is not in excess of the thermal critical point (AC1 point) of the alloy.

While I have mentioned only aluminum as an essential'alloy ingredient, it is to be understood that other elements such as boron, chromium, copper, manganese, molybdenum, nickel, silicon, titanium, tungsten, 'zirconium or vanadium may be present in a combined total amount up to about 8.0% without departing from the true scope and spirit of .my invention.

What I claim is--,

1. An article of manufacture composed of malleableized cast iron having nitride hardened surface portions and containing more than 0.15% and less than 5% of aluminum as an essential alloying ingredient.

2; An article of manufacture composed of malleableized cast iron having nitride hardened surface portions and containing more than 0.15%

aluminum as an essential alloying ingredient.

vrc'roa o. HOMERBERG.

r CERTIFICATE OF CORRECTION.

Patent. No. 1,944,,179a I January 23,, 1934..

VICTOR oi HOMERBERG.

It is hereby certified that error appearsin the printed specification of the above nnmbe'redpatcnt requiring correction as follows: Page 1, line 91, claim 2. for the, words "and less than" read but not over; and that the said Letters Patent should be read with this correction therein that the same may conform to the record or the case in the Patent Office Signed and sealed this 13th day of November, A. D. 1934.

Leslie Frazer (Seal) 7 Acting Commissioner of Patents. 

